Network Virtualization over Layer 3 (NVO3) is a technological framework in cloud computing and network virtualization, referring to an overlay network that provides a Layer 2 (L2) or Layer 3 (L3) service to Tenant Systems over an L3 underlay network using the architecture and protocols as defined by the Internet Engineering Task Force (IETF) NVO3 task force.
L2 and L3 respectively refer to Layer 2 (Data Link Layer) and Layer 3 (Network Layer) services of the Open Systems Interconnection model (OSI Model) comprising 7 layers. The Network Layer (L3) utilizes a data unit of packet, also referred to as a datagram. L3 functions may include structuring and managing a multimode network, including addressing, routing and traffic control. Some examples of L3 protocols are Internet Protocol version 4 (IPv4), Internet Protocol version 6 (IPv6), Internet Protocol Security (IPsec), Datagram Delivery Protocol (DDP) in the AppleTalk suite, and Internet Control Message Protocol (ICMP). The Data Link Layer (L2) utilizes a data unit of bit/frame, to provide services of reliable transmission of data frames between two nodes connected by a physical layer. Some examples of L2 protocols are Point-to-Point Protocol (PPP), IEEE 802.2 Logical Link Control (LLC), Layer 2 Tunneling Protocol (L2TP), and Media Access Control (MAC).
An NVO3 network may be separated from a traditional datacenter network and the Internet. A device and/or a system that connect the NVO3 network with the traditional datacenter network and the Internet should function as a gateway that interfaces with another network using different protocols. Some examples of gateway functionalities include, but are not limited to, protocol conversion, routing, impedance adjustment, rate conversion, fault isolation, signal translation, and any other functionality that negotiates differences amongst networks coupled to the gateway, making the networks interoperable, such as mutually acceptable administrative procedures for both networks, etc. In this specification, one or more computer program that is configured to perform some of aforementioned gateway functionalities is referred to as a gateway, and the gateway runs on a computer system.
As the gateway functionalities are critical in cross-network data communication, the Virtual Router Redundancy Protocol (VRRP) is currently employed to provide uninterrupted gateway functionalities across networks by providing a redundant gateway that may take over a main gateway in case of a failure on the main gateway.